Testing the scattering analysis method for guided waves by means of artificial disturbances

Over the past years, there has been an increasing interest in application of guided waves (Lamb waves) for investigating the damage state of structures. Guided waves propagate over long distances in thin-walled structures and interact even with small damages, e.g., cracks. Consequently, guided waves provide the possibility for wide range inspection in the field of structural health monitoring. In this contribution, the scattering analysis of guided waves is numerically tested by means of artificial disturbances. The setup is defined according to future planned experiments. These artificial disturbances are introduced by circular and square shaped objects with varying thickness and orientation, which are bonded to the surface of an aluminium plate. These small structural obstacles scatter the incident wave. Constructive and destructive interference in the reflections form characteristic patterns, which are described by wave damage interaction coefficients (WDICs). The WDICs are calculated by a local finite element model with non-reflective boundaries (NRB) using the steady-state analysis method. A catalogue of WDICs for the considered artificial disturbances is generated. The local simulation model and the identification method are validated by comparing a transient and a steady-state analysis for the same model. For testing the identification method a global finite element model is simulated for selected damages from the WDIC catalogue by transient analysis, which, however, represent future planned experiments. The transiently simulated scattered time signals at multiple sensing locations are compared to the data from the WDIC catalogue. By this comparison it is shown, that type, thickness and orientation of the considered artificial disturbances can be identified by a comparison of scattered signals to a WDIC catalogue.